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526 Pages·2005·1.34 MB·English

Evidence Report/Technology Assessment

Number 71

Vaginal Birth After Cesarean (VBAC)
Volume 1. Evidence Report and Appendixes

Prepared for:
Agency for Healthcare Research and Quality
U.S. Department of Health and Human Services
2101 East Jefferson Street
Rockville, MD 20852
www.ahrq.gov

Contract Number: 290-97-0018

Prepared by:
Oregon Health & Science University Evidence-based Practice Center
Portland, Oregon

Jeanne-Marie Guise, MD, MPH
Principal Investigator

Marian S. McDonagh, PharmD
Jason Hashima
Dale F. Kraemer, PhD
Karen B. Eden, PhD
Michelle Berlin, MD, MPH
Peggy Nygren, MA
Patricia Osterweil
Kathryn Pyle Krages, AMLS, MA
Mark Helfand, MD, MS

AHRQ Publication No. 03-E018
March 2003
This document is in the public domain and may be used and reprinted without permission except
those copyrighted materials noted for which further reproduction is prohibited without the
specific permission of copyright holders.

Suggested Citation:
Guise J-M, McDonagh M, Hashima J, et al. Vaginal Birth After Cesarean (VBAC). Evidence
Report/Technology Assessment No. 71 (Prepared by the Oregon Health & Science University
Evidence-based Practice Center under Contract No 290-97-0018). AHRQ Publication No. 03-
E018. Rockville, MD: Agency for Healthcare Research and Quality. March 2003.

This report may be used, in whole or in part, as the basis for development of clinical
practice guidelines and other quality enhancement tools, or a basis for reimbursement and
coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement
of such derivative products may not be stated or implied.

AHRQ is the lead Federal agency charged with supporting research designed to improve
the quality of health care, reduce its cost, address patient safety and medical errors, and
broaden access to essential services. AHRQ sponsors and conducts research that provides
evidence-based information on health care outcomes; quality; and cost, use, and access.
The information helps health care decisionmakers—patients and clinicians, health system
leaders, and policymakers—make more informed decisions and improve the quality of
health care services.
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Preface

The Agency for Healthcare Research and Quality (AHRQ), through its Evidence-Based
Practice Centers (EPCs), sponsors the development of evidence reports and technology
assessments to assist public- and private-sector organizations in their efforts to improve the
quality of health care in the United States. The reports and assessments provide organizations
with comprehensive, science-based information on common, costly medical conditions and new
health care technologies. The EPCs systematically review the relevant scientific literature on
topics assigned to them by AHRQ and conduct additional analyses when appropriate prior to
developing their reports and assessments.
To bring the broadest range of experts into the development of evidence reports and health
technology assessments, AHRQ encourages the EPCs to form partnerships and enter into
collaborations with other medical and research organizations. The EPCs work with these partner
organizations to ensure that the evidence reports and technology assessments they produce will
become building blocks for health care quality improvement projects throughout the Nation. The
reports undergo peer review prior to their release.
AHRQ expects that the EPC evidence reports and technology assessments will inform
individual health plans, providers, and purchasers as well as the health care system as a whole by
providing important information to help improve health care quality.
We welcome written comments on this evidence report. They may be sent to: Director,
Center for Practice and Technology Assessment, Agency for Healthcare Research and Quality,
6010 Executive Blvd., Suite 300, Rockville, MD 20852.

Carolyn M. Clancy, M.D. Robert Graham, M.D.
Acting Director Director, Center for Practice and
Agency for Healthcare Research and Quality Technology Assessment
Agency for Healthcare Research and Quality

The authors of this report are responsible for its content. Statements in the report should not be
construed as endorsement by the Agency for Healthcare Research and Quality or the U.S.
Department of Health and Human Services of a particular drug, device, test, treatment, or other
clinical service.

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Acknowledgments

The research team would like to express our regard and appreciation for the efforts of Patty
Davies, MS, for database searching; Benjamin K.S. Chan, MS, for statistical support; A.J.
Mayhew for editing; Susan Wingenfeld, Lynne Schwabe, Nina Mahmud, and James Wallace for
program support; Linda Slattery for administrative support; and everyone else who shared
support and ideas throughout the development of this report. We would also like to thank Rosaly
Correa-de-Araujo, MD, MSc, PhD, of the Agency for Healthcare Research and Quality for her
help as our Task Order Officer.

We also thank the representatives from the American College of Obstetricians and Gynecologists
and the American Academy of Family Physicians, our technical expert panel, our peer reviewers,
and those on the uterine rupture terminology conference call for their invaluable contributions.
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Structured Abstract

Objectives. The literature was systematically reviewed to compare the benefits and harms of a
trial of labor (TOL) and an elective repeat cesarean delivery (ERCD), and to examine factors that
influence decisionmaking.

Search strategy. Published literature on all vaginal birth after cesarean (VBAC) topics was
identified by multiple searches of MEDLINE® (1966 to 2002) and HealthSTAR (1975 to 2002),
from reference lists of systematic reviews, and from local and national experts. Online searches
were performed on Cochrane systematic reviews and controlled trials registry, Centre for
Reviews and Dissemination sites, and EMBASE databases. For topics related to patient
preferences and satisfaction, PsycINFO and CINAHL® databases were also searched.

Selection criteria. Studies begun or published before 1980 and studies that focused on patients
with specific conditions such as gestational diabetes, human immunodeficiency virus,
preeclampsia, and so on were excluded. Studies that exclusively focused on nulliparous women;
vertical, lower vertical, “classical” or “classic” cesarean incisions; vaginal breech delivery;
preterm delivery; multiple gestation; or low birth weight were also excluded.

Data Collection and Analysis. A technical advisory panel provided input from obstetricians,
family physicians, nurse midwives, payers, and patients to ensure that the project addressed
clinical questions and issues. An analytic framework was developed and later refined with input
from national experts and members of the technical panel. The framework relates the 10 topics
reviewed on clinical decision-making for pregnant women with prior cesarean delivery. The
strength and suitability of the evidence regarding the risks of major maternal and infant
morbidity and mortality associated with TOL and ERCD is the main focus of this report. Studies
were rated for quality. We included 180 articles with original data about maternal and infant
outcomes relevant to a key question in one or more topic areas.

Main Results. The literature concerning TOL and ERCD is flawed in several ways: imprecise
measurement of outcomes (e.g., maternal infection, perinatal death), making it difficult to
determine the portion of events directly attributable to maternal choice of delivery route; lack of
standards for terminology (e.g., no standard classification for severity of uterine rupture, nor
attribution specifically to the disruption of the cesarean scar); and limited attention to
comparability between groups (e.g., studies of ERCD where it is unclear whether patients were
eligible for TOL). Similarly, important definitional confounding prevents determination of
whether signs, such as prolonged fetal bradycardia, have any predictive premonitory value.

There is no direct evidence regarding the benefits and harms of TOL relative to ERCD in women
who are similar in every respect except choice of delivery route. Several large cohort studies
provide indirect evidence about relative benefits and harms of TOL versus ERCD. Overall, these
studies report an increased risk of perinatal death and symptomatic uterine rupture of a cesarean
scar with TOL, no increased risk of asymptomatic uterine rupture (dehiscence), maternal death
or hysterectomy from either route, and increased risk of infection from ERCD. However, the
magnitude of risk is uncertain due to methodologic deficiencies of the studies.

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Further studies are needed to test the reliability and usefulness of economic models and
predictive tools.

The literature concerning factors that influence patient decisionmaking and satisfaction with
childbirth was poor, giving us little insights into patient’s priorities.

Conclusions. The deficiencies in the literature about the relative benefits and harms of TOL
versus ERCD are striking. Patients, clinicians, insurers, and policymakers do not have the data
they need to make truly informed decisions about appropriate delivery choices following one of
the most common surgical procedures performed on women. Given the rising prevalence of this
condition, and potential for devastating consequences for thousands of women and children each
year, obtaining accurate data should be a high research priority.

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Agency for Healthcare Research and Quality
Evidence Report/Technology Assessment
Number 71
Vaginal Birth After Cesarean (VBAC)
Summary
Purpose of Report and elective repeat cesarean delivery (ERCD) in
women with prior low transverse of unknown
Target Audience
scar. The scope of the review was to examine
events that were specifically related to having
This report provides a framework for
had a prior CD. Comparisons purely about
comparing the harms and benefits of delivery
vaginal versus cesarean delivery such as
options for women with prior cesarean delivery
incontinence, pelvic support disorders, and
(CD). The information is designed to help
respiratory consequences but not specifically
consumers, providers, payers, and policymakers
about VBAC or repeat cesarean, were not
in decisionmaking about repeat cesarean or trial
considered, though these topics are important to
of labor (TOL).
consider when deciding upon route of delivery.
In judging the suitability of evidence, we took
Overview
the perspective that the first thing a decision-
maker would want to know is whether the risk
In 2000, 22.9 percent of all births in the
of these complications is higher for a trial of
United States occurred by CD. This rate is the
labor, versus an elective cesarean delivery, under
highest total CD rate reported since data
optimal conditions of care. That is, the most
collection began in 1989. The vaginal birth after
relevant evidence would compare the outcomes
cesarean (VBAC) rate, defined as the proportion
and risks of a properly managed trial of labor to
of women with a prior CD who delivered
that of a properly conducted elective cesarean
vaginally, steadily increased from 1989 to 1996.
delivery. Some components of obstetric care, as
As allowing TOL became more common,
well as some aspects of the setting of this care,
practice variation became a larger concern, e.g.,
might increase the risks of TOL or ERCD. For
expanding criteria for eligibility and medical
example, it has been hypothesized that the use
induction, and for augmentation of labor. In
(or misuse) of drugs for induction and
parallel with this liberalization of criteria and
augmentation might increase the risk of uterine
management, highly publicized articles
rupture in patients who have had a prior
suggested that maternal and fetal risks were
cesarean delivery. We examined the strength of
perceived to be increasing. Subsequently, the
evidence that these factors influence these
VBAC rate has decreased 27 percent from 1996
outcomes and adverse effects and to what extent
to 2000. Currently, a crisis in malpractice rates
these factors can explain the results of
is decreasing the availability of maternity care
observational studies of VBAC complications.
providers and raising concerns that patients may
have limited options, less access to care, and
perhaps be at increased risk for complications. Methodology
Reporting the Evidence Key Questions
The strength and suitability of the evidence Two types of key questions were addressed.
regarding the risks of major maternal and infant The first group (Questions 1- 7) compares the
morbidity and mortality associated with TOL or outcomes of a TOL and an ERCD:
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES • Public Health Service
1. What is the frequency of vaginal delivery in women who preeclampsia, and so on. Exclusions were also made for
undergo a TOL (spontaneous onset, induced, and studies that focused primarily on the following: nulliparous
augmented) after prior low transverse cesarean or women, vertical, lower vertical, “classical” or “classic” cesarean,
unknown scar? vaginal breech delivery, preterm delivery, multiple gestation, or
2. How accurate are risk assessment tools for identifying low birth weight.
patients who will have a vaginal delivery after a TOL? Two investigators reviewed a random set of titles and
abstracts for each topic to select articles for full-text review.
3. What are the relative harms associated with a TOL
When an appropriate level of reliability was reached for
(spontaneous onset, induced, and augmented) and repeat
inclusion and exclusion of studies, the primary investigator
cesarean?
reviewed the remaining titles and abstracts on the topic.
4. What is the incidence of uterine rupture, and are there
Investigators read the full-text version of the retrieved papers
methods for preventing major morbidity and mortality
and reapplied the initial eligibility criteria. Data from 224
due to uterine rupture?
studies were abstracted and included in the evidence tables
5. What are the health status and health-related quality of described in the results section of this report.
life for VBAC and repeat cesarean patients?
Data Abstraction
6. Regarding VBAC and repeat cesarean, what factors
influence patient satisfaction/dissatisfaction with their
Included study designs were determined by topic area.
childbirth experience?
Study designs of included articles consisted of randomized
7. How are economic outcomes related to VBAC, repeat controlled trials, cohort studies, case-control studies, cross-
CD, and their respective complications? sectional studies, large case series (more than 10 subjects), and
The second group (Questions 8-10) address factors economic or decision models. All data were abstracted by the
influencing the decision to have a TOL: lead investigator for the topic. If the lead investigator
encountered difficulty in finding or interpreting information
8. What individual factors influence route of delivery?
in the published report, a second investigator reviewed the
9. What factors influence a patient’s decisionmaking article and a consensus was reached.
regarding VBAC or ERCD?
Assessment of Study Quality
10. How do legislation, policy, guidelines, provider
characteristics, insurance type, and access to care affect
To assess the internal validity of individual studies, we
health outcomes for VBAC candidates? applied a set of design-specific criteria developed by the
Relevant studies were identified from multiple searches of current U.S. Preventive Services Task Force and additional
MEDLINE® (1966 to 2002) and HealthSTAR (1975 to criteria developed by the NHS Centre for Reviews and
2002), from the reference lists of systematic reviews and from Dissemination, based at the University of York in England. In
local and national experts. The online Cochrane systematic general, studies were rated good if they met all criteria, fair if
reviews and controlled trials registries, DARE, National they addressed some but not all criteria, and poor if they had a
Centre for Reviews and Dissemination, and EMBASE “fatal flaw.” Investigators were asked to use the study quality
databases were searched for relevant literature on specific ratings as previously described to determine for their topic
topics as well. For topics related to patient preferences and which quality components were most important in assessing
satisfaction, PsycINFO and CINAHL® databases were internal validity. This process allowed for some individual
searched. Databases were searched twice during the course of topic fit for fatal flaws, etc. A second investigator
the project, with the final search in March 2002. For all independently rated all included articles, and disagreements
VBAC topics combined, 14,449 citations were retrieved, were resolved by consensus.
including 4,867 about spontaneous labor and uterine rupture,
Data Synthesis
2,528 about ERCD, 2,416 about induction of labor, 2,945
citations about predictors, 1,257 about patient satisfaction,
Where appropriate, meta-analysis was performed using
preference and health status, and 436 about cost and access.
WinBugs® or StatsDirect® software. To reduce potential bias,
All searches were limited to English-language articles only studies of fair or good quality were included in the
published since 1980 (the date of the NIH Consensus analyses.
Conference on VBAC) in developed countries. The report
focused on studies that identified a group of patients with
Findings
prior cesarean. For patient preferences and satisfaction, studies
of the general birthing population, were considered if there
Question 1. Likelihood of Vaginal Delivery
were no studies that identified patients with prior cesarean.
Studies were excluded if they focused on patients with
• Rates of vaginal delivery when attempting TOL ranged
particular conditions such as gestational diabetes, HIV,
from 60 to 82 percent. The largest population-based
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study reported a rate of 60.4 percent. The combined • No studies examined specifically the risks of incontinence
vaginal delivery rate for all prospective cohort studies, or pelvic support disorders in women with prior cesarean.
largely conducted in tertiary care centers and University • Rates of infection were increased in ERCD versus TOL
settings, was 75.9 percent. overall. Studies that performed subgroup analyses for
• There are limited data on the effect of medical induction TOL with and without vaginal delivery consistently
and augmentation of labor. found increased rates of infection for women who
• There was a 10-percent reduction in the likelihood of attempted TOL but ultimately had a cesarean delivery.
vaginal delivery when oxytocin was used for ether • There is conflicting evidence regarding whether
induction or augmentation. There was a similar trend in induction of labor affects infection rates.
reduced likelihood of vaginal delivery with
Infant
prostaglandins.
• There is insufficient evidence regarding the effect of
Question 2. Predictive Tools
selected route of delivery and Apgar score or respiratory
morbidity.
• Two validated scoring systems categorized women into
• No study measured infant death directly attributable to a
groups with likelihoods of vaginal delivery ranging from
mother’s choice of TOL or repeat CD.
roughly 45 to 95 percent.
• There is uncertainty about the magnitude of risk of
• One tool was able to stratify more of the population (up
perinatal death due to TOL. Results from two large
to 50 percent of women choosing TOL) into high and
studies differ in the magnitude of increased risk from
low probability subgroups, with a relatively low false-
TOL versus ERCD (90/1,000 TOL versus 50/1,000
positive rate.
ERCD compared with 12.9/1,000 TOL versus 1.1/1,000
• By using a prospective cohort design and the largest
ERCD). Neither study provides direct evidence of risk.
study population, the best scoring system created a 10-
point score based on the presence or absence of five
Question 4. Uterine Rupture
variables commonly available for most patient
admissions.
• The use of terms among studies is inconsistent.
• An RCT clearly demonstrated the inability of X-ray
• Definitions among studies for similar terms are
pelvimetry (XRP) to predict route of delivery reliably.
ambiguous.
• Imaging studies that combined the measurements of the
• There is no difference in asymptomatic uterine rupture
pelvis and fetus showed promising results, but were
rates in TOL versus ERCD.
limited by their lack of control for confounding and
• Symptomatic uterine rupture is significantly more
biases.
common in TOL versus ERCD, with an increased risk of
Question 3. Maternal and Infant 2.7/1000.
Outcomes
• Based on the frequency and severity of symptomatic
uterine rupture, the risk of perinatal death due to a
General
rupture of a uterine scar is 1.5/10,000 and the risk of
• In the absence of RCTs of TOL versus repeat cesarean, maternal hysterectomy is 4.8/10,000. These rates of
evidence that is most generalizable comes from large serious complications such as perinatal death are probably
country, State, or regional population-based studies more precise than overall risks from studies measuring
(referred to as population-based studies) followed by large death directly.
multicenter cohort studies, large single-institution or
• The definition of uterine rupture as an outcome is
single-practice cohort studies, then smaller cohort studies,
confounded by a definition that includes the potential
respectively.
predictor of fetal heart rate (FHR) tracing abnormality.
• There is no direct evidence regarding the benefits and
• Measurement of frequency of occurrence, predictors for
harms of TOL relative to ECRD in women who are
what population is at greatest risk, and predictors for
similar in every respect except choice of delivery route.
poor outcomes are not possible, because of the lack of
• Several fair and good quality studies provide indirect
standard case definition.
evidence about relative benefits and harms of each route.
Maternal Question 5. Health Status
• Maternal death rates did not differ between TOL and
• There were no studies of health status or health-related
ERCD.
quality of life for VBAC or repeat CD patients.
• The best evidence suggests that hysterectomy rates do not
differ between TOL and ERCD.
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Question 6. Patient Satisfaction • A woman’s choice for delivery was often based on social
motives (e.g., easier recovery, so she can care for baby and
• Studies of patient satisfaction largely consisted of the children at home).
patient’s own provider obtaining information about • Only four of 11 studies cited safety for mother or baby as
patient satisfaction, introducing the possibility of important reasons for delivery choice.
measurement bias.
• It remains unclear whether VBAC education increases the
• Only two cross-sectional studies used methods other than proportion of women who choose TOL.
the patient’s own provider to obtain satisfaction
information. Question 10. Legal, Provider, Hospital,
• No study measured satisfaction for the three types of Insurance Characteristics
delivery outcomes that could be experienced by women
General
with prior CDs (VBAC, TOL followed by CD, or
ERCD). • Studies of legislation, policy, guidelines, hospital
characteristics, provider characteristics, insurance type, or
Question 7. Cost and Health Care access to care focus exclusively on VBAC rates rather than
Resources safety.
Legal
• For a TOL success probability of 76 percent or greater,
• No study provides direct evidence for the impact of
TOL is more cost-effective and provides higher quality of
malpractice issues on VBAC or ERCD.
life.
• Further evaluation is needed of the sensitivity of the • One study reported that VBAC rates increased when
legislation was enacted that standardized VBAC
probability cut point of 76 percent to other potential
guidelines had to be provided to obstetric providers.
predictor variables.
• The best evidence suggests that use of opinion leaders
Question 8. Individual Factors provides a greater likelihood of changing practice
compared with audit and feedback.
• The vast majority of studies looking at individual factors
Provider
that influence the route of delivery were of poor quality
• Studies of provider characteristics failed to control for
due to the lack of control for confounding factors.
important variables such as patient selection bias.
• The factors that were significantly associated with an
increased likelihood of vaginal delivery (i.e., successful Hospital
TOL) were maternal age less than 40 years, prior vaginal • VBAC rates were higher in teaching hospitals compared
delivery (particularly vaginal delivery after cesarean), a to private, community, regional, or non-teaching
nonrecurrent indication for the prior CD, and favorable hospitals.
cervical factors.
• Three studies conflicted over the effect of hospitals
• The factors that were significantly associated with a containing a neonatal intensive care unit (NICU).
decreased likelihood of vaginal delivery (i.e., failed TOL)
Insurance
were an increasing number of prior CD, gestational age
greater than 40 weeks, birthweight greater than 4000 g, • There was conflicting evidence regarding whether
and augmentation of labor. insurance status predicts VBAC.
Question 9. Patient Preferences
Summary of Evidence
• Patient preferences for birth choice are unclear because of
the heterogeneity of the 11 included studies. The following summarizes the type of study design, the
quality of the evidence from studies, and the suitability of the
• Several factors appear related to choice for TOL (White
study design to answer the particular question for each key
race, prior vaginal delivery, lower levels of anxiety during
question.
the pregnancy).
• Lack of medical information along with cultural
ideologies might account for minority women being less
likely to attempt a TOL when compared with White
women.
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